不同污染天气下大气颗粒物及化学成分干沉降通量的粒径演变特征OA北大核心CSTPCD

Wet and dry deposition processes are the major removal mechanisms for atmospheric pollutants and are important sources of nutrients and toxins in ecosystems.Compared to wet deposition,dry deposition is more difficult to measure directly;thus,an inferential approach is often used to estimate dry deposition fluxes.In this study,size-resolved particle dry deposition velocities(Vd)were calculated using classical parameterization,which was then combined with measured size-and chemically resolved ambient concentrations to estimate the dry deposition fluxes of particulate matter,with a focus on heavy pollution days.The calculated size-resolved Vd of particulate matter varied from 0.037 to 0.50 cm·s-1,with increased values at high wind speeds and low relative humidity.The maximum and minimum values of Vd occurred at 5.8‒9 μm and 0.65‒1.1 μm or 1.1‒2.1 μm,respectively.With a minimum Vd value at a particle size of 1.1 μm,Vd increased as the particle size decreased or increased,reflecting the different dominant microphysical mechanisms of dry deposition for different particle sizes.During the observation period,dry deposition fluxes of particulate matter ranged from 9.41 to 108.71 mg·m-2·d-1,with a mean value of 36.65 mg·m-2·d-1.The concentration and Vd had a greater influence on the dry deposition fluxes of the coarse and fine particles,respectively.During heavy polluted days,the dry deposition fluxes of particles at each size range showed an upward trend,among which the dry deposition of secondary aerosols of nitrate,sulfate and ammoniums showed an obvious"size distribution shift"phenomenon.Such a phenomenon occurred in both January 2013 and January 2022,indicating that persistent heavily polluted weather in the North China Plain may increase the input of particulate species to the surface ecosystem through dry deposition.